A species of periodical cicada expected to remain underground for 17 years has begun popping up in some areas of the United States – and, they’re four years early.

Sightings of Brood X cicadas this spring have been reported from Maryland to Tennessee, with as many as 1,000 spotted in the span of just two days.

While it’s not entirely unusual to see some cicadas coming out early, scientists suspect climate change could be speeding up their growth, causing them to emerge in much higher numbers years before their time.

A species of periodical cicada expected to remain underground for 17 years has begun popping up in some areas of the United States – and, they’re four years early. Sightings of Brood X cicadas (pictured) this spring have been reported from Maryland to Tennessee

THE LIFE-CYCLE OF A 'PERIODICAL' CICADA

While ‘annual’ cicadas may be spotted every summer, cicadas belonging to the genus Magicicada are known to follow either a 13-year or 17-year cycle.

These creatures remain underground for years, feeding off the roots of trees.

It’s thought that they keep track of time by ‘counting’ the seasonal cycles, possibly through the flow and quality of xylem sap in the trees, according to Cicada Mania.

Once the nymphs have grown big enough, they emerge when the soil temperature at 8-inches deep reaches 64 degrees Fahrenheit.

This typically occurs in May, or sometimes as early as April.

The nymphs then climb out and molt one last time, to mate above ground.

It’s thought that cicadas ‘count’ the passing years in sets of four, meaning those in a 17-year brood may emerge four years early if they’ve grown big enough by that point, the Washington Post reports.

The Brood X cicadas are expected to come out to reproduce in 2021, after 17 years feeding on plant roots beneath the surface.

This year is supposed to be when Brood VI emerges, with the phenomenon already underway in Georgia and the Carolinas.

But, Brood VI has been joined by some Brood X ‘stragglers,’ experts say.

‘Periodical cicadas often emerge in years before or after they are expected to emerge,’ according to Cicada Mania.

Share this article

This normally occurs by May, according to Cicada Mania, but can sometimes take place in April when temperatures are unseasonably warm.

And, as temperatures for the season continue to get warmer with each passing week, more are expected to emerge.

The Brood X cicadas are expected to come out to reproduce in 2021. This year is supposed to be when Brood VI emerges, with the phenomenon already underway in Georgia and the Carolinas. But, Brood VI has been joined by some Brood X ‘stragglers,’ experts say

While it’s not entirely unusual to see some cicadas coming out early, scientists suspect climate change could be speeding up their growth, causing them to emerge in much higher numbers years before their time

Scientists keep track of citizens’ cicada sightings using the site Magicicada.org, which launched roughly a decade ago.

Now, they’re wondering if increased internet capabilities have allowed for more reports in recent years – or, if climate change is causing emergence patterns to shift.

‘You could see many more individuals coming out four years early, and eventually those could become so numerous that they’re self-reproducing,’ Chris Simon, professor of ecology and evolutionary biology at the University of Connecticut told the Washington Post.

‘If the conditions are really good, then a lot of them will come out.

‘The longer the growing season, the higher the chance that a very large number will be ready four years early.’